A pointer variable is an object that can point to another object. Here int *ptr = NULL; declares ptr as a pointer object, that potentially points to an object of int.

The value initially stored into this pointer object is NULL (it is initialized to NULL, so ptr does not point to any object).

Now, ptr too resides in memory. It needs enough bytes to contain the address of the pointed-to object. So it too needs to have an address. Therefore

  • ptr evaluates to the address of object that ptr points to.
  • &ptr evaluates to the location of the ptr object itself in memory
  • *ptr evaluates to the value of the object that ptr points to, if it points to an object. If it does not point to an object, then the behaviour is undefined.

Also, %p needs a void * as the corresponding argument, therefore the proper way to print them is

printf("%p\n", (void *)ptr);
printf("%p\n", (void *)&ptr);
Answer from Antti Haapala on Stack Overflow
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freeCodeCamp
freecodecamp.org › news › a-quick-and-thorough-guide-to-null-what-it-is-and-how-you-should-use-it-d170cea62840
A quick and thorough guide to ‘null’: what it is, and how you should use it
June 12, 2018 - We intuitively associate a precise meaning to null. In a simple and flawless world, null would simply mean that Alice actually doesn't have an email address.
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Quora
quora.com › In-computer-programming-what-is-the-address-of-null-in-memory
In computer programming, what is the address of null in memory? - Quora
Answer (1 of 4): If you’re talking about the value null (or NUL, or 0), a byte in which all bits are 0, any memory address could potentially point to a byte with this value. So, the address of a NUL byte could potentially be any memory address.
Discussions
c - Address of NULL pointer - Stack Overflow
So your pointer address is 0x7ff..., and its value is null, iow zero. ... Find the answer to your question by asking. Ask question ... See similar questions with these tags. ... Is the “freezing” of infalling matter at a black hole horizon purely observational, or does it have physical meaning? More on stackoverflow.com
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c - What is the value of a NULL address location? - Stack Overflow
So incrementing a pointer by one unit means incrementing it's value by sizeof(int). Also, you aren't printing the value of which pointer is directing (as this would certainly crash your program) but the value of the pointer itself. You should definitely take a look at any pointers tutorial in C (or in general). ... thanks a lot , does it really point to the first address location when we point to NULL ... More on stackoverflow.com
🌐 stackoverflow.com
June 10, 2012
What is Null?
This was intended as a meme but is actually a good representation of what "Null" is. In C#, when you declare string s = "My shit"; it means that "s" is a reference to a memory location that holds the data "My shit". string s = null; means that the reference "s" exists but it's not pointing to any object, as in it holds nothing. More on reddit.com
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July 5, 2024
What does the word "null" appear in front… - Apple Community
Alert symbol What does a yellow ... point in the middle mean? This shows up almost immediately when I try to access my new mail & defaults to error page. HELP!!! 361 1 ... This message it usually means that your reply-to address may be labeled wrong. One place to start is Mail>Window>Previous Recipients ... This thread has been closed by the system or the community team. You may vote for any posts you find helpful, or search the Community for additional answers. What does the word "null" appear in ... More on discussions.apple.com
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May 9, 2018
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Education Ecosystem
educationecosystem.com › home › what is the null address in crypto?
What is the Null Address in Crypto? Null Address in Crypto
January 3, 2022 - Standard addresses are just a string ... On the other hand, a null address is an address created specifically to receive tokens that are being intentionally removed out of circulation....
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BitKan
bitkan.com › learn › what-is-null-address-in-crypto-is-null-address-the-same-as-vanity-address-9530
What is NULL address in crypto? Is null address the same as vanity address?
Null addresses in encryption are generated specifically to allow proof-of-burn. Token burns occur when tokens are intentionally sent to unusable wallets to remove them from circulation. This address is called the burn address or diner address.
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Wordtothewise
wordtothewise.com › 2019 › 09 › null-sender-address
Null sender address | Word to the Wise
September 12, 2019 - If the 5321.from is the SPF domain and there is an entire class of email that doesn’t have a 5321.from, what do we do about SPF? Never fear, the SPF spec addresses that. When the message has a null from address, the domain in the HELO is checked for a SPF record.
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Chainargos
docs.chainargos.com › documentation › concept-glossary › address-types › null-address
Null Address | Concept Glossary | ChainArgos
May 13, 2024 - Consequently the convention used for most blockchains is to use a string consisting entirely of 0s – know as the “null address” – to indicate “unknown private keys.” That string was clearly not randomly generated.
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Stack Overflow
stackoverflow.com › questions › 46871763 › address-of-null-pointer
c - Address of NULL pointer - Stack Overflow
Top answer
1 of 3
12

A pointer variable is an object that can point to another object. Here int *ptr = NULL; declares ptr as a pointer object, that potentially points to an object of int.

The value initially stored into this pointer object is NULL (it is initialized to NULL, so ptr does not point to any object).

Now, ptr too resides in memory. It needs enough bytes to contain the address of the pointed-to object. So it too needs to have an address. Therefore

  • ptr evaluates to the address of object that ptr points to.
  • &ptr evaluates to the location of the ptr object itself in memory
  • *ptr evaluates to the value of the object that ptr points to, if it points to an object. If it does not point to an object, then the behaviour is undefined.

Also, %p needs a void * as the corresponding argument, therefore the proper way to print them is

printf("%p\n", (void *)ptr);
printf("%p\n", (void *)&ptr);
2 of 3
7

ptr holds the value NULL which is what you assigned.

&ptr is the address to the variable ptr which in your case is 0x7fff3415dc40

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Quora
quora.com › Are-there-special-addresses-like-null-where-nothing-is-stored
Are there special addresses (like null) where nothing is stored? - Quora
Answer (1 of 3): Any address that is treated as NULL (or nullptr) by the compiler is special. Usually NULL points to address 0, but some systems have NULL point to other addresses.
Find elsewhere
🌐
MDN Web Docs
developer.mozilla.org › en-US › docs › Glossary › Null
Null - Glossary - MDN Web Docs
In computer science, a null value represents a reference that points, generally intentionally, to a nonexistent or invalid object or address. The meaning of a null reference varies among language implementations.
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Stack Overflow
stackoverflow.com › questions › 10969808 › what-is-the-value-of-a-null-address-location
c - What is the value of a NULL address location? - Stack Overflow
Top answer
1 of 5
9

You're setting a pointer to 0 (NULL) and then adding 1 to it; then you're converting the result to an int and printing the result. The key piece of knowledge you need here is that when you increment (add 1 to) a pointer, you actually add the size of the pointed-to object -- an int pointer is advanced to point to the next int. Since int is (apparently) 4 bytes on your platform, p is incremented to point to an address 4 bytes past where it starts.

2 of 5
3

Size of the int in C is (typically) 4 bytes. So incrementing a pointer by one unit means incrementing it's value by sizeof(int).

Also, you aren't printing the value of which pointer is directing (as this would certainly crash your program) but the value of the pointer itself. You should definitely take a look at any pointers tutorial in C (or in general).

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Reddit
reddit.com › r/learnprogramming › what is null?
r/learnprogramming on Reddit: What is Null?
July 5, 2024 -

So I use C# and I often see many devs use null.

What and which kind of situation do you use this variable?

I am reading c# guide on programming book and I am on Clearing memory now and I haven't encountered null yet. Should I be worried?

Top answer
1 of 18
80
This was intended as a meme but is actually a good representation of what "Null" is. In C#, when you declare string s = "My shit"; it means that "s" is a reference to a memory location that holds the data "My shit". string s = null; means that the reference "s" exists but it's not pointing to any object, as in it holds nothing.
2 of 18
15
NULL is nothing. It means theres nothing there. Often its just a place holder before something is there. Say u have a bunch of variables of animals. U might set them to NULL before u know what they are. Then u might check if they are NULL before u add an animal to them. Things are initialized as NULL.
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Apple Community
discussions.apple.com › thread › 8384331
What does the word "null" appear in front… - Apple Community
Top answer
1 of 1
4
This message it usually means that your reply-to address may be labeled wrong.One place to start is Mail>Window>Previous Recipients
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TutorialsPoint
tutorialspoint.com › why-is-address-zero-used-for-the-null-pointer-in-c-cplusplus
NULL Pointer in C
A NULL pointer in C is a pointer that doesn't point to any of the memory locations. The NULL constant is defined in the header files stdio.h, stddef.h as well as stdlib.h. A pointer is initialized to NULL to avoid the unpredicted behavior of a
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PixelPlex
pixelplex.io › home › glossary › zero address
Zero address Definition
May 23, 2025 - The zero address, also known as the null address, refers to a special blockchain address that consists entirely of zeros (e.g., 0x0000000000000000000000000000000000000000 in Ethereum-like systems).
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VIPRE Helpdesk
helpdesk.vipre.com › hc › en-us › articles › 36698500494609-Null-Senders
Null Senders – VIPRE Helpdesk
June 30, 2025 - The Envelope-From is used by mail servers to determine where bounce messages should be sent if the email cannot be delivered. A null sender, as the name suggests, has an empty or null Envelope-From address.You can find more information on the ...
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Medium
medium.com › @shlomohassid › null-how-do-you-define-nothing-and-why-would-you-07683bdbe63a
NULL: How Do You Define Nothing? And Why Would You? | by Momi | Medium
May 31, 2025 - If you had an array of 1000 null ... values. NULL doesn’t mean “nothing stored here” – it means “stored here is a token that signifies no target.”...
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Stack Exchange
ethereum.stackexchange.com › questions › 117476 › ethereum-null-address-list
etherscan - Ethereum Null Address List - Ethereum Stack Exchange
Top answer
1 of 1
3

In general, yeah you can choose any arbitrary address that you want for null address.

The reason you can do that is because it is almost impossible for you to choose a random address that somebody already has a private key for it. Let's do some math to prove it, an address is 256 which mean it can go up to 2^256. The earth population at this time (12/2021) is about 7.9 billion but i will make it 8 billion for ease in calculation. Assume every person in the planet has 100 private key corresponding to the address they have. Then the possiblity that you can choose an address that they already choosen is about 10^-66 (https://www.wolframalpha.com/input/?i=800%2C000%2C000%2C000+%2F+2%5E256).

The possiblity that you win a Powerball is one in 292.2 million, roughly 10^-9 (https://www.thebalance.com/what-are-the-odds-of-winning-the-lottery-3306232). So you will have to win Powerball roughly 7 times in a row to even get a chance in picking a random address that somebody already has the private key given that everybody on the earth have 100 private keys

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Scaler
scaler.com › home › topics › what is null pointer in c?
What is Null Pointer in C? - Scaler Topics
September 4, 2023 - A null pointer is a special reserved value declared in a header file called stddef. Null indicates that the pointer is pointing to the first memory location. meaning that 0th location.
🌐
Etherscan
etherscan.io › address › 0x0000000000000000000000000000000000000000
Null: 0x000...000 | Address: 0x00000000...000000000 | Etherscan
This address is not owned by any user, is often associated with token burn & mint/genesis events and used as a generic null address
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Quora
quora.com › What-does-NULL-mean-in-programming-languages
What does NULL mean in programming languages? - Quora
Answer (1 of 6): null is the pointer or reference to address zero. Why would this be needed or used? Let’s say you are searching for a library book that you want to read. Unlike Amazon, your library doesn’t have every book.
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